5Hybrid RF and BB beamformingJanuary 2015Hybrid RF and BB beamformingIt is possible to create a MIMO system by combining multiple RF signals in one BB through a hybrid beamforming scheme. Two approaches are possible:Relatively simple modification of IEEE802.11ad to support multi-stream transmission on the base of several arraysNew antenna + RF design with maximal antenna aperture for both streamsAlexander Maltsev, Intel

6Hybrid beamforming: two stages – RF and BBJanuary 2015Hybrid beamforming: two stages – RF and BBHybrid beamforming consists of two stages: Coarse (RF) and Fine (BB) beamformingCoarse beamforming: sector sweep in RF to establish one or several independent links (rays) between TX and RX antennasFine beamforming: optimal weighting done in BB in accordance with given criterionSet of channels after coarse beamforming between different TX-RX beams may be treated as a virtual MIMO channel, and well-known MIMO techniques can be applied to those channelsAlexander Maltsev, Intel

16SISO vs. MIMO comparison, big pictureJanuary 2015SISO vs. MIMO comparison, big pictureFor apple-to-apple comparison between the SISO and MIMO we need not only set up equal TX power, but also the identical antenna configurationsThe SISO system on the base of two 2x8 arrays (2x16 elements array) shows the same performance as 2x2 MIMO at large distances (SVD produces [1; 1] beamforming vectors for TX and RX)On the distances less than 30-40m the MIMO processing gives more capacity than SISO with the same antenna system configuration.Alexander Maltsev, Intel

17January 2015ConclusionThe OFDM-MIMO system with hybrid beamforming analyzed for wireless docking station scenario for omni and directional, co-polarized and cross- polarized antennas in free space and typical office environments.The implementation of the 2x2 MIMO on the base of omni antennas is problematic due signal weakness and fading effects.For free space, the 2x2 MIMO on the base of 2x8 antenna arrays provides double peak rate at the distances up to 10 m for both co-polarized and cross-polarized antennas.For typical Wireless Docking usage the 2x2 MIMO on the base of 2x8 antenna arrays provides double peak rate at the distances up to 10 m, but reflected rays interference may cause deep fading gaps at certain distances for both co-polarized and cross-polarized antennas.With identical antenna systems MIMO scheme with 2x2 Hybrid RF and BB beamforming gives more capacity than SISO scheme with RF beamforming only for distances up to 30-40m, that can be exploited in AP type usages.Alexander Maltsev, Intel